1. Field of the Invention
The invention generally relates to hot oil fryers for the continuous hot oil frying of large quantities of food products as in large scale food process lines. More particularly, the invention relates to improvements in sediment removal from the cooking oil, for extending the use life of the cooking oil; as well as, reduced height heat exchanger banks that permit a shallower oil level in the cooking channel, and hence reduce the quantity of cooking oil needed to fill the system. Additional aspects and objects of the invention will be apparent in connection with the discussion further below of preferred embodiments and examples.
2. Prior Art
FIG. 1 shows a representative deep fat fryer 18 in accordance with the prior art. It's for the continuous deep fat frying of large quantities of food product in a large scale food process line. The apparatus as generally shown by FIG. 1 is more particularly depicted and described in connection with U.S. Pat. No. 5,074,199--Miller, owned by Stein, Inc., of Sandusky, Ohio. That patent reference is incorporated herein by this reference to it. The vantage point of FIG. 1 is aimed at the discharge end of the fryer apparatus 18. Hence with reference to FIG. 1, the fryer apparatus 18 comprises a rigid unitary frame or housing 20. The frame 20 extends axially from the discharge end to the infeed end of the apparatus 18, and extends vertically up from the floor to the level of apron members 21. The apron members 21 are directly secured to the top of the frame 20 and are connected in a unitary manner with a lining which forms an elongated horizontal oil tank or "cooking channel" 22.
The cooking channel 22 is defined by front and rear walls, spaced side walls and a bottom wall (eg., the bottom wall is indicated as 22.sup.1 in FIG. 3). FIG. 7 gives another view of a cooking channel. The cooking channel will hold a volume of cooking liquid or oil (eg., or sometimes else known as "fat," as in "deep `fat` frying"). The frame 20 includes feet 20a.
Mounted near the four corners of the fryer apparatus 18 are four upright jacks 23. The jacks 23 are preferably hydraulic and likely incorporate vertically extending piston rods 23a. The piston rods 23a are connected at their upper ends to respective cross bars 24a and 24b. Wherein, cross bar 24a is near the infeed end of the apparatus (ie., the far end in FIG. 1) and cross bar 24b is near the discharge end (ie, the near end in FIG. 1). Mounted above these cross bars 24a and 24b is an elongated hood or cover 25. The hood or cover 25 has a rectangular recess or opening 25a at its lower side which makes a generally close fit with the aprons 21 when the apparatus 18 is in its nested or "closed" position for a cooking operation as illustrated in FIG. 2. The hood 25 may be provided with exhausts or vents (not shown) for exhausting gases or venting steam produced in association with the frying operation.
The fryer 18 includes a pair of cooperating conveyors 26 and 30, wherein the overhead conveyor 26 is a "submerger" conveyor and the underneath conveyor 30 is the main tractor or food-carrying conveyor. Frying food product (not shown) is transported through the cooking channel 22 compressed between these two conveyors 26 and 30.
The submerger conveyor 26 has spaced parallel outer side rails 26a. It is suspended as shown in FIG. 1 by its outer side rails 26a hanging on a set of four (4) relatively short chains 27. One pair of the chains 27 is connected to the cross bar 24a at the infeed end of the fryer 18, and the other pair of the chains 27 is connected to the cross bar 24b at the discharge end. The main tractor or food-carrying conveyor 30 has spaced parallel outer side rails 30a, and it is suspended by its outer side rails 30a hanging from a set of four (4) relatively longer chains 31. A pair of these relatively longer chains 31 is connected with the cross bar 24a near the infeed end of the fryer 18 as the two other of the relatively longer chains 31 are connected with the cross bar 24b near the discharge end of the fryer.
Reference may be had to an early U.S. Pat. No. 3,757,672--Szabrak et al., for a more detailed discussion of the fryer 18's construction and operation, which patent reference of Szabrak, et al., is also incorporated herein by this reference to it. Basically, main tractor conveyor has an upper, food-carrying run 30.sup.1 (as well as a lower return run 30.sup.2). The submerger conveyor 26 has a lower, food-submerging run 26.sup.1 (in addition to its upper return run 26.sup.2). In use, the upper or food-carrying run 30.sup.1 of the main tractor conveyor 30 supports the food product during transport through the cooking channel 22 concurrently as the lower or food-submerging run 26.sup.1 of the submerger conveyor 26 presses the food product down sufficiently to keep it from floating off.
To maintain compression between the food-carrying run 30.sup.1 and the food-submerging run 26.sup.1 of conveyors 30 and 26, respectively, requires reinforcement being given to both runs 30.sup.1 and 26.sup.1. FIG. 2 shows that the opposed runs 30.sup.1 and 26.sup.1 are oppositely reinforced. That is, the food-carrying run 30.sup.1 is reinforced by a beds of rollers 32 whereas the food-submerging run 26.sup.1 is reinforced by a ceiling of like rollers.
FIG. 1 shows the fryer 18 in an open position. The side rails 30a of the main conveyor 30 are hoisted up well above and out of the hot bath of oil in the cooking channel 22. The side rails 26a of the submerger conveyor 26 are hoisted up even higher, as over the main conveyor 30. The hood 25 is shown disposed elevated even above the submerger conveyor rails 26a. This open position of the fryer 18 as shown by FIG. 1 allows the manual clearing of food product blockage from the conveyors, or more generally, the open position facilitates inspection, cleaning and maintenance.
FIGS. 2 and 3 do not strictly depict the same fryer configuration 18 as shown by FIG. 1. More particularly, the fryer 18' of FIGS. 2 and 3 is adapted from a pair of patent references which are commonly owned by Stein, Inc., consisting of not only the aforementioned U.S. Pat. Nos. 5,074,199--Miller, but also 5,253,567--Gunawardena, which latter patent reference is likewise incorporated by this reference to it.
The predominant distinction between the FIG. 1 fryer 18 and the FIGS. 2,3 fryer 18' relates to location of the heat exchanger units 36,38 relative to the main tractor conveyor 30. In FIG. 1, the heat exchanger units 36,38 are situated completely below both runs 30.sup.1 and 30.sup.2 of the main tractor conveyor 30. In FIGS. 2 and 3, the heat exchanger units 36,38 are situated between the two runs 30.sup.1 and 30.sup.2 of the main tractor conveyor 30. Indeed, in FIGS. 2 and 3, the lower or return run 30.sup.2 scrapes along the bottom 22.sup.1 wall of the cooking channel 22.
With more particular reference to FIGS. 2 and 3, the fryer apparatus 18' includes fore and aft heat exchanger units or "banks" 36 and 38 of what are known as indirect-fired type heat exchangers. Unlike direct-fired types (wherein the heat exchangers are actually flues venting the combustion gases of a combustion source), indirect-fired heat exchangers circulate a recycled hot medium that is heated by a remote combustion or heat source 44. Preferably the circulating hot medium is another oil or else steam:--oil is probably more common because it is less difficult to manage than steam.
The forward heat exchanger bank 36 occupies the front or infeed half of the cooking channel 22 as the aft bank 38 is situated in the rear or discharge half of the cooking channel 22. The heat exchanger banks 36 and 38 are adapted for heating the bath of cooking oil or fat within the cooking channel 22 to a desired temperature (eg., .about.400.degree. F.-500.degree. F.). In use, the heat exchange units 36 and 38 are submerged in the deep fat bath of the fryer.
Each heat exchange bank or unit 36 or 38 comprises a plurality of vertically oriented heat transfer "plates" 40. Although, these "plates" 40 are actually vessels that have hollow cores which define a flow channel therein. As shown by FIGS. 2 and 3, the bank or banks of heat exchangers 36,38 are positioned below the roller bed 32 of the main food carrying run 30.sup.1 of the main conveyor 30, and above the return run 30.sup.2 thereof. Each heat-exchanger bank 36,38 has an inlet manifold 42 and inlet piping 44a on one extremity and an outlet manifold 42 and outlet piping 46a at its opposing extremity. The inlet and outlet manifolds 42 are coupled to each of the heat exchanger plates 40 to uniformly introduce the re-circulating hot medium to each.
The design of the heat-exchanger "plates" 40 can partly be reckoned from inspection of FIG. 2. No doubt, the design of the heat-exchanger "plates" 40 is more particularly described and depicted in the aforementioned patent reference of Gunawardena. But with reference to FIG. 2, each heat exchanger plate 40 typically comprises at least two sheets of stainless which are secured together to form a pressurized vessel. The opposite sheets may be "dimpled" together in places by tack weld or, that is, employ a double embossed design which has inflated zones on both sides. In this manner, a plurality of pockets are formed such that the core or flow passage in any given plate-like vessel 40 causes the circulating hot medium to split into separate tendrils, which tendrils are directed to braid and intertwine with one another through the course of the flow passage. The sheets are sealed by welding about their edges to form such a hollow "plate"40.
The heat-exchanger plates 40 are generally vertically oriented on edge and spaced laterally across the width of the cooking channel 22. Also, the plates 40 are connected at each end by the inlet manifold 42/44a and exit manifold 42/46a, respectively. The vertical, on-edge orientation of the plates 40 and the spacing therebetween permits bread crumbs or food particles to fall through. That is, bread crumbs or other sediment which falls through the food-carrying run 30.sup.1 as well as the bed of rollers 32, ought to get clearance between the vertical plates 40 to land on the bottom wall 22.sup.1 of the cooking channel 22. The return run 30.sup.2 of the main conveyor 30 will motivate or push such sediment along the bottom wall 22.sup.1 of the cooking channel 22 (see, eg., FIG. 3) with the intention that such sediment will ultimately be removed from the oil system by a sediment-discharge auger 48.
FIG. 3 shows diagrammatically that the return or sediment-transporting run 30.sup.2 of the main food conveyor 30 indeed travels fairly closely along the bottom wall 22.sup.1 of the cooking channel 22. Hence the return or sediment-transporting run 30.sup.2 catches and facilitates removal of sediments comprising food particles which have fallen from food products on the main food-carrying run 30.sup.1 and sunk to the bottom 22.sup.1 of the cooking channel 22. These types of sediment materials are removed from the fryer 18' by means of the sediment-carrying run 30.sup.2 pushing the sediment along the bottom 22.sup.1 of the cooking channel 22 until the cooking channel 22 opens into a sediment-removal well 22.sup.2. The sediment-removal well 22.sup.2 is positioned at the discharge end of the return or sediment-transporting run 30.sup.2. The sediment-removal well 22 has a deep end which is occupied by the discharge auger 48.
The main food conveyor 30--including its main food-carrying run 30.sup.1 and sediment-transporting return run 30.sup.2 --is typically formed from an endless conveyor belt constructed of a wire mesh, as shown by for example, FIG. 6. Such a wire mesh belt is driven by conventional means such as a chain drive or hydraulic system and the like.
The fryer 18 is likely provided with sensors associated with the housing 20 and/or hood member 25, which in conjunction with an electronic control system (not shown) will indicate whether the hood 25 is in a closed position to enable operation of the apparatus, or whether hood 25 is opened which will render the apparatus inoperative for safety purposes. Other sensors (not shown) associated with the apparatus 18 may include a low oil level sensor and temperature sensors to allow precise control of temperature of the cooking oil throughout the cooking cycle within the apparatus 18. Additional safety features associated with the apparatus 18 may comprise high temperature cutoff or limiting switches flame sensors or the like which will automatically shut down operation of the apparatus upon the occurrence of unsafe conditions in its operation. An electronic control system may be used to control all of the various aspects of operation of the fryer apparatus accordingly.
Shortcomings with prior art fryer apparatus relate to the excessive volume of cooking oil required to charge the oil system at one time, as well as to sediment removal. It is desirable to minimize the charge or volume of cooking oil needed to keep the fryer in service during use, as much as practicable. In other words, it is desirable to get by on as low of cooking oil volume as practicable. The prior art design of the heat exchanger plates 40 has the flattened plate-like pressure vessels sitting on edge to present a relatively tall aspect that must be all submerged by cooking oil. And then, at an elevation above the heat exchangers, an intervening bed of rollers which support the food-carrying run from sagging spread out the distance between the source of heat (ie., the heat exchangers) and the sink of heat (ie., the food product transiting on the food-carrying run of the conveyor). Cooking oil must be poured into the channel to support this intervening bed of support rollers too.
Minimizing cooling oil volume is important for large scale food processing applications for a variety of reasons. With a low volume of cooking oil, it is easier to keep the cooking oil in circulation. Sediments might be more efficiently strained and filtered out of the cooking oil. Also, poor oil circulation within the fryer tank and/or cooking channel creates hot spots which affords decomposition of the oil, and/or rises in the free fatty acids. Un-removed sediments which char in the hot oil contribute further to decomposition of the oil, with a greater likelihood of unpleasant tasting food products. Once that happens, the cooking oil must be changed out, with the old oil being discarded. The replacement of the cooking oil is one cost users of frying apparatus would like to minimize because simply, the cost of replacement cooking can add up and be significant over time. Just as importantly, users would like to avoid or minimize the down time that the whole food process line suffers because of the hold-up associated with a change-out of the cooking oil in the fryer.
What is needed is an improvement which overcomes the shortcomings of the prior art.